Patent Literature 1 discloses a stacked polymer electrolyte battery that includes a short-circuiting and heat radiation accelerating unit formed by arranging two metal plates with an insulator therebetween outside a stacked electrode group. According to the battery disclosed in Patent Literature 1, it is believed that when electrodes short-circuit in nail penetration testing on the battery etc., passing a short-circuit current through the short-circuiting and heat radiation accelerating unit can reduce voltage of electric elements, and makes it possible to smoothly radiate heat generated in the unit etc., to the outside. Patent Literatures 2 to 4 also disclose various techniques for suppressing heat generation caused by short circuits inside batteries due to nail penetration etc.